The present invention relates to an improved pressure communicating system for subsea wellhead annuli.
Recently the Minerals Management Service has issued new rules and regulations affecting oil and gas operations in the Outer Continental Shelf. (See Federal Register Apr. 1, 1988, pp. 10596 through 10777 and particularly 10730 through 10733). These rules include the requirement that it is necessary in such subsea wellheads to be able to monitor all annuli for pressure.
The disclosure of one prior patent (U.S. Pat. No. 4,116,044, issued Sept. 26, 1974) suggest the monitoring of a plurality of annuli within a wellhead at an unaccessible location by having pressure sensors extending through the wall of the wellhead to communicate with the annuli therein. These sensors are used to detect packoff leaks by detecting change of pressure under the seal after the area above the seal is pressurized. These sensors are connected to a junction box and to the surface to provide indication of the output of the sensors.
U.S. Pat. No. 4,410,186 issued Oct. 18, 1983, discloses a combination leakage detection system with a sealant injection system for pressurized flanged joints. The flanges include passages through the ring seal and through the flanges to provide for the detection of leakage and the maintenance of the seal.
U.S. Pat. No. 4,458,903, issued July 10, 1984, discloses a special tubular member to seal a control passage across a flanged joint. The control passage is stated as being applicable to subsurface safety valves. The tubular seal extends between flanges to provide a sealed continuation of the passage extending through the lower member and the passage extending through the upper flange to a needle control valve on its exterior.
U.S. Pat. No. 4,202,410, issued May 13, 1980, discloses a seal testing system for a wellhead joint in which test passages extend through the walls of the wellhead to the exterior to provide the indication of the pressure in the annulus to which each passage is connected.
U.S. Pat. No. 3,974,690, issued Aug. 17, 1976, discloses the sensing of vertical movement of a pressure responsive element to detect the change of pressure in an annulus. This involves lowering a sensing head into the wellhead to sense the position of the movable element and thus determine the pressure to which it has been exposed.